Crystal structure and reactivity of mononuclear cationic palladium(II) andplatinum(II) triphos complexes with phenyltin(IV) anions. The formation ofpolynuclear platinum-triphos ionic and covalent complexes

The ionic complexes [M(triphos)Cl]X [M = Pd, X = Cl (1), SnCl3 (1a), SnPh2C l3 (1c); M = Pt, X = Cl (3), SnCl3 (3a), SnPh2Cl3 (3c)], [M(triphos)Cl](2)X [X = SnPh2Cl4, M = Pd (1b), Pt (3b); X = PtCl4, M = Pt (3d)] and [M(tripho s)(2)]X-2 [X = SnPh2Cl3, M = Pd (2), Pt (4)] where triphos = bis(2-diphenyl phosphinoethyl)phenylphosphine, were synthesised and characterised by micro analysis, mass spectrometry, IR, Sn-119 Mossbauer, NMR (P-31, Pt-195 and Sn -119) spectroscopies and conductivity measurements. The X-ray crystal struc tures of compounds 1b, 3b and 3c, where tetrachlorodiphenylstannate(IV) and trichlorodiphenylstannate(IV) act as counterions stabilising cationic meta l complexes, are reported. These compounds contain the cation [M(triphos)Cl ](4) with distorted square-planar geometry at palladium or platinum, tripho s acting as a tridentate chelating ligand. The anions [SnPh2Cl4](2-) (1b, 3 b) and [SnPh2Cl3](-) (3c) have trans-octahedral and distorted trigonal-bipy ramidal environments for the metal, respectively. Although the dinegatively charged [SnPh2Cl4](2-) is counteracted by the presence of two singularly p ositively charged [M(triphos)Cl](+) species, interanion contacts via hydrog en bonds were found for Ib and 3b but were absent for compound 3c. The crys talline solids [M(triphos)(2)][SnPh2Cl3](2) [M = Pd (2), Pt (4)] were forme d via a chelate ring-opening reaction of [M(triphos)Cl](+) induced by triph os. The formation of heterometallic complexes by reaction of AgCl or Au(I) with the complex [Pt(triphos)(2)][SnPh2Cl3](2) (4), followed by P-31 NMR in solution, did not take place. The presence of dangling arm phosphine oxide groups, on oxidation of complex 4 with H2O2, was detected. Other ring-open ing reactions were observed by P-31 NMR and conductivity measurements when solutions containing PtC1(2)(PhCN)(2) and triphos in a molar ratio 3:2 were refluxed C,H,. Besides [Pt(triphos)Cl](2)[PtCl4] (3d) and the ionic comple x with a dinuclear anion, [Pt(triphos)Cl][Pt-2(triphos)Cl-5] (5). the coval ent trinuclear complexes [{PtCl2(Ph2PCH2CH2)(2)PPh-P-1,P-2} (2)(P-3,P-3)PtC l2] (6a, 6b) were formed as minor products. These latter diastereomeric spe cies become the dominant species upon heating, being thermodynamically cont rolled complexes. Mixtures of 3d, 5, 6a and 6b converted to complex [Pt(tri phos)Cl]Cl (3) by addition of triphos, chelate ring-closure reactions of 6a , 6b and the complex anion 5 occurring. With an excess of triphos (Pt:triph os = 3:4 or higher ratio), broad peaks reflecting fast equilibria between r ing-opened and ring-closed products were found. (C) 2001 Elsevier Science L td. All rights reserved.